Sewage treatment plant

ABSTRACT

The invention relates to a sewage treatment plant for treatment of waste fluid, said plant comprising at least one aeration chamber ( 2, 3 ), a settling chamber ( 4 ) and a disinfection chamber ( 5 ). In order to rationalize the layout and the structure of the sewage treatment plant ( 1 ), the at least one aeration chamber ( 2,3 ) and the settling chamber ( 4 ) are arranged in a structural unit comprising opposite end walls ( 101, 102 ), opposite side walls ( 103, 104 ), a bottom part ( 105 ) and a cover part ( 106 ). The disinfection chamber ( 5 ) is arranged separately outside one of said end walls ( 101, 102 ), side walls ( 103, 104 ), bottom part ( 105 ) or cover part ( 106 ) of the structural unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase of International ApplicationNo. PCT/FI02/00922 filed on Nov. 20, 2002 and published in English asInternational Publication No. WO 03/048053 A1 on Jun. 12, 2003, whichapplication claims priority to Finnish Application No. 20012366 filed onDec. 3, 2001.

The invention relates to a sewage treatment plant for treatment of wastefluid according to the preamble of claim 1.

Sewage treatment plants for treatment of waste fluid are well known inthe art. In previously known sewage treatment plants waste fluid isfirstly led to an aeration chamber by way of gravity or vacuum. Thenumber of aeration chambers may vary, however, often one or two aerationchambers are sufficient to provide a desired aerobic treatment. From theaeration chamber the aerated waste fluid is forwarded to a settlingchamber, where sludge is separated from the waste fluid, wherebyclarified waste fluid is led to a disinfection chamber, where thetreatment is finalised by chemical treatment.

The configuration and structure of known closed sewage treatment plantsare most often very complex since the function of the various chambersset specific requirements also to the features of the individualchambers. Furthermore, the chambers usually are in fluid communicationwith each other through piping and thereto related pump means. Theassembly and manufacturing of known treatment plants is thus verydifficult. Secondly, the disinfection chamber is usually arranged in thesame body as the other chambers, whereby the aerobic and chemicalenvironments are mixed. The sewage treatment plant, due to the qualitiesof the sewage, also requires a high degree surface treatment of theinternal surfaces subject to the sewage, which is made very difficultdue to the complex structure and the mixed environments.

The object of the present invention is to provide a sewage treatmentplant, by which the above disadvantages are avoided and which providesan efficiently and reliably operating device. This object is attained bya sewage treatment plant according to claim 1.

The basic idea of the invention is to rationalize the layout andstructure of the treatment plant in View of the treatment process andits requirements. In the present invention the at least one aerationchamber and the settling chamber are arranged in a closed, substantiallyrectangular structural unit, or body, comprising opposite end walls,opposite side walls, a bottom part and a cover part, whereas thedisinfection chamber is arranged outside one of said side walls, endwalls, bottom part or cover part of the structural unit. In this way theaeration chamber(s) and the settling chamber, which are in the same sizecategory, are arranged in one module operating in a common separatedaerobic environment. The disinfection chamber, which usually issubstantially smaller than the other chambers, is located outside theaerobic module, whereby it forms a separate chemical environment in acorresponding manner. This allows for minimizing the risk of chemical,usually chlorine, contamination of the aerobic environment. Furthermore,the surface treatment of the inside of the aerobic module and thechemical module can be arranged separately, as well as respectivemaintenance access.

By arranging the settling chamber at one end of the structural unit withan end wall portion forming one end wall of the structural unit andcomprising at least a lower part which is inclined, the flow directionof the waste fluid is in sequence with the treatment steps. Secondly,the specific placing of the inclined wall portion facilitates assemblyand surface treatment. Also, the inclined outer wall of the settlingchamber, i.e. the body of the sewage treatment plant, may be placed nearthe side or the stern of a marine vessel, which usually have inclinedconfigurations in these areas. This allows for efficient use of spaceaboard a marine vessel. Marine vessels are typical applications whereclosed sewage treatment plants are used.

The lower part of the end wall portion of the settling chamber isinclined and the angle of inclination of the end wall portion isadvantageously about 45° to 70°, preferably about 55° to 65°. It hassurprisingly shown that these inclination or slope values are sufficientin view of the settling stage, in which activated sludge is separatedfrom the clarified waste fluid.

The disinfection chamber is advantageously arranged at the end wallportion of the settling chamber, forming an end wall of the structuralunit, or a side wall portion of the settling chamber, forming a part ofa side wall of the structural unit, whereby the aforementioned flowsequence can be followed.

The end wall portion or the respective side wall portion of the settlingchamber, between the settling chamber and the disinfection chamber, isprovided with an aperture for overflow of waste fluid. In this way therisks arising from mixing the aerobic environment and the chemicalenvironment may be minimized.

The width of the disinfection chamber is advantageously smaller than thedepth of the settling chamber, i.e. the end wall portion of the settlingchamber, or the width of the settling chamber, i.e. the respective sidewall portion of the settling chamber, and the height of the disinfectionchamber is limited to an area above the inclined lower part of the endwall portion of the settling chamber. Further, the disinfection chamberis advantageously provided with a releasable cover portion, whichfacilitates assembly and maintenance.

A further advantageous feature of the sewage treatment plant accordingto the invention is that the cover part is releasably fastened to thestructural unit, preferably with bolt or screw means. This furtherfacilitates manufacture and assembly, including surface treatment of theinside of the unit, as well as maintenance, since the separate chamberscan easily be accessed.

The sewage treatment plant is advantageously divided into partitions byat least one partition wall in order to form the at least one aerationchamber and the settling chamber. An opening is provided between thepartition wall or walls and the cover part of the structural unit foroverflow of waste fluid. This facilitates manufacture and assembly, andas the aerobic and chemical environments are separated, any possiblyback-flow or splashing remains within the aerobic environment. This isespecially advantageous e.g. on a marine vessel (discussed above) whichis subject to rolling at sea. With this arrangement it is alsosufficient with one common ventilation means for the aerobicenvironment.

The above discussed chamber arrangement is advantageous since it allowsfor forwarding the waste fluid from chamber to chamber by naturaloverflow instead of using piping and pump means as in the prior artsolutions.

By arranging any necessary reinforcement structures outside the body ofthe sewage treatment plant, i.e. the structural unit, the inner surfacesof the chambers can be kept as plane as possible, which facilitatesmanufacture, assembly and maintenance.

The so-called closed sewage treatment plant according to the presentinvention is designed for treating so-called black water (waste fluidfrom toilets, urinals, hospital facilities) and so-called gray water(waste fluid from galleys, showers, wash basins, sinks), and isparticularly advantageous for marine applications, i.e. marine vessels,in connection with which strict requirements relating to sewage and thedischarge of the same prevail.

In the following the invention will be described more in detail, by wayof example only, with reference to the accompanying schematic drawings,in which:

FIG. 1 shows a flow diagram principle for the sewage treatment plant;

FIG. 2 shows a perspective view of the sewage treatment plant; and

FIG. 3 shows a sectional view of the sewage treatment plant.

The flow diagram shown in FIG. 1 is only intended to describe thetreatment process of the sewage treatment plant according to the presentinvention in a general manner. The sewage treatment plant is indicatedby reference numeral 1. The sewage treatment plant 1 comprises fourchambers, i.e. a first aeration chamber 2, a second aeration chamber 3,a settling chamber 4 and a disinfection chamber 5 provided with adisinfectant dosage system 6.

Waste fluid is supplied to the first aeration chamber 2 through line 7,indicated as an inlet port 7 in connection with FIG. 2, by way ofgravity or vacuum. From the first aeration chamber 2 treated waste fluidis led to the second aeration chamber 3 by way of overflow indicated byline 8. In order to stimulate bacterial growth air is supplied to thefirst and second aeration chambers 2 and 3 by means of e.g. a blower Aor fan through lines 9 and 10, which lead to air distribution means 11and 12 arranged in the bottom area of the first and second aerationchambers 2 and 3.

From the second aeration chamber 3 the aerobically treated waste fluidis led to the settling chamber 4 by way of overflow indicated by line13. When the treated waste fluid arrives in the settling chamber 4,activated sludge is separated by gravity by settling on the inclined endwall portion 14 of the settling chamber 4. Remaining activated sludgemay be returned from the settling chamber 4 to the first aerationchamber 2 for renewed treatment through the return line 19. Byconnecting the air line 24 to the return line 19, the feedback of sludgecan be arranged to be carried out by way of an ejector effect.

The first aeration chamber 2, the second aeration chamber 3 and thesettling chamber 4 may advantageously be provided with a common airventilation means 116 (FIG. 2) since these chambers are arranged in thesame closed aerobic environment, as will also be discussed below inconnection with FIGS. 2 and 3.

The sewage treatment plant may provide a sufficient treatment resultwith only one aeration chamber. The advantage with two aeration chambersis, however, that the aeration process can be carried out in two phases,a rougher phase and a subsequent finer phase, generally improving theresult. Secondly, if one of the aeration chambers needs maintenance, thesewage treatment plant may still function adequately with only the otheraeration chamber. Also, if one of the aeration chambers has to becompletely drained, the bacterial strain is not completely destroyed asit remains in the other chamber. This is an important aspect sinceregeneration of bacterial strain may take a number of weeks.

The waste fluid is subjected to almost complete aerobic-biologicaldegradation during its flow through the first three chambers. Thus, theclarified fluid in the settling chamber 4 may finally be led to thedisinfection chamber 5 by way of overflow as indicated by line 15. Thedisinfection chamber 5 is supplied with disinfectant from a dosagesystem generally indicated by reference numeral 6 and line 16. Acommonly used disinfectant is e.g. a chlorine based disinfectingchemical. The clarified and disinfected waste fluid may then bedischarged from the disinfection chamber by discharge means, e.g. a pumpmeans P, indicated on line 20.

Disinfection may also be supplemented by UV radiation, whereby the UVradiation system can be arranged in connection with the disinfectionchamber or the above mentioned discharge means.

The purpose of disinfection is to eradicate bacteria.

Mineralized sludge may also be removed from the first and secondaeration chambers 2 and 3 as indicated by lines 17 and 18. The firstaeration chamber 2, the second aeration chamber 3 and the settlingchamber 4 are advantageously also provided with separate drain means 21,22 and 23.

FIGS. 2 and 3 show the sewage treatment plant 1, or more particularlythe body of the same, from a more constructional viewpoint. The sewagetreatment plant 1 comprises the first and second aeration chambers 2 and3 and the settling chamber 4 arranged after each other in the structuralunit or body of the sewage treatment plant, the chambers thus beingarranged one after the other in the flow order or sequence of the wastefluid.

The structural unit comprises opposite end walls 101 and 102, oppositeside walls 103 and 104, a bottom part 105 and a cover part 106 forming aclosed entity having a substantially rectangular configuration. Thefirst aeration chamber 2, the second aeration chamber 3 and the settlingchamber 4 are formed within this substantially rectangular body by afirst partition wall 107 and a second partition wall 108.

The disinfection chamber 5 is, in FIG. 2, shown to be arranged on theoutside of the one side wall 104 of the structural unit, at a side wallportion 104 a of the settling chamber 4. The disinfection chamber 5could be arranged outside any one of said side walls 103, 104, end walls101, 102, bottom part 105 or cover part 106 as desired. In view of theflow sequence, particularly the overflow process, one of the side wallportions 103 a, 104 a or the end wall portion 101 a of the settlingchamber 4 is be preferable.

In the following the disinfection chamber 5 will be discussed asarranged on one side wall portion 104 a. However, it is clear thatcorresponding arrangements may be applied even with other positionings,whereby adequate flow arrangements, including piping when necessary,have to be provided.

The positioning of the disinfection chamber may be chosen according tothe application or location of the sewage treatment plant, as well asaccording to availability of space.

The end wall portion 101 a of the settling chamber 4, which also formsone of the end walls 101 of the structural unit, has an inclined lowerpart 14 for the settling process in this chamber. The angle α ofinclination, i.e. between the plane of the bottom part 105 and the planeof inclined lower part 14, is advantageously about 45° to 70°,preferably about 55° to 65°. The angle α of inclination is to somedegree dependent on the dimensions of the settling chamber 4. There areclear constructional and space requirement advantages in having only oneinclined surface, opposed to a theoretically ideal, with regard to thesettling process, funnel form, which shall be discussed more in detailbelow.

Waste fluid is supplied to the first aeration chamber 2 through theinlet port 7, indicated as line 7 in FIG. 1, for a first aeration phase.The overflow of waste fluid from the first aeration chamber 2 to thesecond aeration chamber 3, and further to the settling chamber 4, mayadvantageously be attained by providing a first opening 109 and a secondopening 110 between the first partition wall 107 and the cover part 106and the second partition wall 108 and the cover part 106. In practicethis may e.g. be realized by giving the first partition wall 107 aheight H1 less than the inner height H of the structural unit and thesecond partition wall 108 a height H2 less than the height H1 of thefirst partition wall 107, whereby a so-called natural overflow isachieved. The relative heights discussed above have to be dimensioned sothat an appropriate degree of overflow is established. These chambersthus form a common and open aerobic environment within the structuralunit separate from the chemical environment formed by the disinfectionchamber 5.

Overflow from the settling chamber 4 to the disinfection chamber isarranged by providing an aperture 111 in the side wall portion 104 a ofthe settling chamber 4, which aperture 111 opens directly into thedisinfection chamber 5.

One or more of the chambers may be provided with high and low levelmonitoring means according to need, e.g. for securing the overflowfunction and to provide for a reliable treatment process.

The cover part 106 of the structural unit may be provided with only onecommon ventilation means 116 for the first and second aeration chambers2 and 3 and the settling chamber 4 since these form a common and closedaerobic environment.

The disinfection chamber 5, which forms a chemical environment, is onlyin contact with the aerobic environment through the overflow aperture111, which thus minimizes the risks of contamination of the aerobicenvironment by the chemical environment. The disinfection chamber 5 isusually also of a relatively smaller size than the other chambers, as isschematically indicated in FIG. 2. It is usually sufficient that thewidth of the disinfection chamber 5 is smaller than the width of thesettling chamber 4, or the side wall portion 104 a of the settlingchamber 4, whereby the height of the disinfection chamber 5, due toconstructional reasons may be limited to an area above the inclinedlower part 14 of the end wall portion 104 of the settling chamber 4. Thevolume of the disinfection chamber 4 may then be varied by the depth Dof the disinfection chamber.

The disinfection chamber is provided with a cover portion 115, which maybe arranged to be fastened to the side wall of the disinfection chamber5 with bolt or screw means 120. An additional advantage with theseparation of the disinfection chamber 5 from the rest of the chambersis that sedimentation, which usually accumulates during the disinfectionstage and has a negative effect on the cleaning process, easily can beremoved.

The cover part 106 may further be provided with a first cover portion112, a second cover portion 113 and a third cover portion 114 foraccessing the first aeration chamber 2, the second aeration chamber 3and the settling chamber 4 respectively, e.g. for provisionalmaintenance of or sample testing from the individual chambers. The coverportion 106 is advantageously fastened to the structural unit by bolt orscrew means 117, advantageously by having a peripheral flange portion118 arranged around the upper edges of the end walls 101 and 102 and theside walls 103 and 104 of the structural unit.

The structural unit is can easily be reinforced by arrangingreinforcement structures, such as ribs 119, on the outer sides of theend and side walls 101, 102, 103 and 104, as well as the bottom part 105and the cover part 106 of the structural unit. Corresponding measuresmay also be taken with the disinfection chamber 5 when necessary. Thereinforcement structures 119 are shown on only one side wall 104 of thestructural unit, by way of example only. However, it is to be understoodthat they can be applied on any outside surfaces, if and when foundnecessary.

The constructional advantages of the sewage treatment plant according tothe invention are, in addition to what has been indicated above, asfollows. First of all, the end walls 101 and 102, the side walls 103 and104, the bottom part 105 and the cover part 106, which also constitutethe respective portions, e.g. 101 a, 103 a and 104 a, of the individualchambers, including the inclined lower part 14 of the end wall portion101 a of the settling chamber 4, may be manufactured from metal platesor sheets, which can be welded together. Access to the inside weldingspots is facilitated by the releasably fastenable cover part 106 of thestructural unit as well as the only one inclined wall portion 14 of thesettling chamber 4. This also facilitates adequate inside surfacetreatment of these components, having clearly exposed surfaces, which isextremely important with regard to the substances treated in the sewagetreatment plant and their corrosive effect.

This also concerns the disinfection chamber 5 in a corresponding manner.

The plain design also facilitates installation of additional components,such as pipes, pipe mountings, grids, etc.

The above description and the drawings relating thereto are onlyintended for clarifying the basic idea of the invention. The inventionmay vary in detail within the scope of the ensuing claims.

1. Sewage treatment plant for treatment of waste fluid, said plantcomprising at least one aeration chamber, a settling chamber, and adisinfection chamber, wherein the at least one aeration chamber and thesettling chamber are arranged one after the other in the flow order ofthe waste fluid in a structural unit, which comprises opposite endwalls, opposite side walls, a bottom part, at least one partition wallin order to form the at least one aeration chamber and the settlingchamber such that the chambers form a common aerobic environment, and acover part releasably fastenable to the structural unit in order to formthe common aerobic environment and arranged to provide access to the atleast one aeration chamber and the settling chamber when the cover partis removed; and wherein the disinfection chamber is arranged outside thestructural unit, on an end wall portion of the settling chamber or on aside wall portion of the settling chamber; and the disinfection chamberis provided with a releasably fastenable cover portion.
 2. Sewagetreatment plant according to claim 1 wherein the end wall portion of thesettling chamber, which forms an end wall of the structural unit,comprises at least a lower pan which is inclined.
 3. Sewage treatmentplant according to claim 2 wherein the lower part of the end wallportion of the settling chamber is inclined and the angle (α) ofinclination is about 45° to 70°, preferably about 55° to 65°.
 4. Sewagetreatment unit according to claim 1 wherein the end wall portion or therespective side wall portion of the settling chamber, between thesettling chamber and the disinfection chamber, is provided with anaperture for overflow of waste fluid.
 5. Sewage treatment plantaccording to claim 4 wherein the width of the disinfection chamber issmaller than the depth of the settling chamber, i.e., the end wallportion of the settling chamber, or the width of the settling chamber,i.e., a side wall portion of the settling chamber, and the height of thedisinfection chamber is limited to an area above the inclined lower partof the end wall portion of the settling chamber.
 6. Sewage treatmentplant according to claim 1 wherein the cover part of the structural unitis releasably fastenable to the structural unit with bolt or screwmeans.
 7. Sewage treatment plant according to claim 1 wherein the coverposition of the disinfection chamber is releasably fastenable to thedisinfection chamber by bolt or screw means.
 8. Sewage treatment unitaccording to claim 1 wherein an opening is provided between the upperedge of the partition wall or walls and the cover part of the structuralunit for overflow of waste fluid.
 9. Sewage treatment plant according toclaim 1 wherein the structural unit is provided with one or morereinforcement structures and reinforcement structures are arranged onthe outside of said walls and parts.